Sheila Jackson Lee is so deeply entrenched in her congressional seat, knocking her off her throne is pretty close to mission impossible.

She won her post 24 years ago after downtown power brokers — notably Enron CEO Ken Lay — abandoned then-congressman Craig Washington over his opposition to NAFTA and the space station. Since then Jackson Lee has become legendary for her aggressive self-promotion, whether it's speaking at Michael Jackson's funeral or planting herself on the aisle before State of the Union speeches to get her picture on television shaking the president's hand.

But even Democratic politicos who joke about her insatiable appetite for camera time have come to respect Jackson Lee as a hardworking voice for progressive causes. With almost a quarter-century of seniority, she now serves on the House Judiciary, Homeland Security and Budget committees. She likes to brag about her role in securing federal funds for a wide range of needs — from education to veteran services — for constituents in her district.

The 18th Congressional District, gerrymandered by GOP mapmakers to pack as many Democrats as possible into its boundaries, stretches from Sunnyside to the Heights to Acres Homes and Greenspoint. So if anybody's ever going to beat Jackson Lee, it would almost certainly have to be another Democrat running against her in a primary. That's the role assumed in this election cycle by Richard Johnson, 57, an education administrator who has worked on the staffs of elected officials in the Texas Legislature and Houston city council.

Jackson Lee, 68, has her liabilities. Most notably, her brusque management style has earned her a reputation as one of the worst bosses on Capitol Hill. Stories abound about Jackson Lee's high-handed use of staffers to run personal errands and chauffeur her around Washington. Small wonder she's been criticized for having one of the highest staff turnovers in Congress.

But Johnson offers no compelling reason for Democratic primary voters to choose him over Jackson Lee. During their appearance before our editorial board, the incumbent consistently showed a deeper awareness of a broad range of issues. She has an inherent advantage, given her decades of experience in Congress. Johnson, on the other hand, seemed so focused on vocational education — an issue he was comfortable discussing because he worked it on as a Legislative staffer in Austin — he sounded like a better candidate for a community college board.

Between these two candidates, the obvious choice for Democratic primary voters is Sheila Jackson Lee.